This invention relates generally to a novel method and apparatus for adjusting the lateral position of special purpose lenses on eyeglasses and fixing the lenses, once so adjusted, against undesired lateral motion of the lenses with respect to the eyeglass frame.
In the prior art there have been basically four different means by which lenses have been secured to frames for eyeglasses. First it has been common to cement the lens to a portion of the frame. A second common method has been to pin the lens directly to the frame, for example, as is done with rimless eye glasses. A third common method has been to form a ridge, as by grinding, around at least a portion of the periphery of the lens and to fit that ridge into a female groove in the eyeglass frame or into a female grooved member which fits over the frame and the ridge of the lens. Finally, it is known to provide a female groove around the periphery of the lens and insert a wire-like member therein which forms a part of the frame.
Each of the above methods perform quite well under some specific applications for the wearers of eye glasses. However, with respect, e.g., to cataract lens wearers, there are some very unique and specific requirements. A cataract lens must be adjustable with respect to the supporting system formed by the eyeglass frame and the lens supporting members to permit positioning of the lens so that the center of the lens is directly over the pupil of the wearer. Lateral displacement of the lens which varies the optical center from its desired position with respect to the frame, as little as 0.5 mm can have an effect on the vision of the wearer and more significant displacements rapidly deteriorate the effectiveness of the cataract lens causing improper vision and eye strain of the wearer. Therefore, once properly positioned, the lens must also be securely affixed to the frame in such a manner that it will not move, particularly laterally.
The outer periphery of the cataract lens must be as near a knife edge as possible, and there must be no optical obstruction along that knife edge. That is, the frame cannot extend around the outer periphery of the lens along the knife edge. If there is any obstruction along the knife edge, it causes extreme interference with the vision of the wearer.
Finally, the temple piece must be as far removed from the line of vision as possible.
Each of the lens systems in the prior art possess some of the features required for a cataract lens wearer or wearer of other lenses requiring fitting to the wearer. None of them have all of the features. The lens attaching methods and apparatus of the prior art leave significant room for improvement when it comes to fixing a lens to the eyeglass frame and preventing any lateral movement whatever, while still allowing easy adjustment of the lens position for a particular wearer prior to fixing its final position.
The patents to Gitlin et al., U.S. Pat. Nos. 3,565,517, Feb. 23, 1971 and 3,475,083, Oct. 28, 1969, and to Stolper, 3,017,806, Jan. 23, 1962, and the French Pat. No. 1,347,120, Nov. 18, 1963, show a form of a locking cavity contained in a portion of lens-holding part of the eyeglass frame or formed between two detachable parts of the eyeglass frame. They do not show an attaching method and apparatus in which the lateral position of the lens with respect to the frame is adjustable to fit the needed lens position for a specific wearer of the glasses, which is required for certain special purpose lenses, e.g., cataract lenses.
In addition, Stolper shows a portion of the attaching means extending along the outer periphery of the lens, which is not suitable for cataract lenses. Further, in the magnetic lens holding means shown in the Gitlin et al. patents, the magnet is not sufficient to provide positive prohibition of lateral motion with respect to the frame, so that, even if the Gitlin et al. patent disclosures were expanded beyond their teaching to provide that the flange on the lens support member was shorter than the groove in the frame, thus allowing lateral adjustment during fitting, the lens would not be positively held against lateral motion by the magnet holding means.
The lens holding means shown in the patent to Bernheim, U.S. Pat. No. 2,529,068, Nov. 7, 1950 suffers from the same defects of not providing for lateral adjustability during fitting and extension of the holding means along a portion of the outer periphery of the lens. It is also readily apparent that the means for holding the lenses in the goggles discussed in the patent to Peloquin, U.S. Pat. No. 1,573,088, Feb. 16, 1926, is totally incapable of achieving the desired results of the present invention.
Lenses having a generally keystone shaped portion which fits into a grooved portion on the eyeglass frame or a grooved portion of a plastic member which fits over the frame and keystone are known as is shown, e.g., in the patents to Williams, U.S. Pat. Nos. 2,091,296, Aug. 31, 1937; 2,198,852, Apr. 30, 1940; and 2,384,867, Sept. 18, 1945.
These patents disclose a lens holding device in which the lens is prevented from lateral movement either by being cemented in the groove or by having a metal or plastic extension of the groove which extends beyond the end of the keystone of the lens and which is either bent over or heat formed around the end of the keystone to prevent lateral motion.
There is no suggestion in any of the Williams' patents noted above of adjusting the position at which the metal or plastic extension of the groove is bent or heat formed in order to vary the lateral position of the optical center of the lens according to the specific "fit" of a wearer of special purpose lenses, e.g., cataract lenses. There is also no suggestion of the keystone having a length less than the length of the groove on the lens frame or plastic member in order to allow lateral adjustment to a specific wearer. In addition, cementing the lens in the grove creates problems in adjusting the lens to a specific wearer, as discussed below with respect to another method and apparatus used in the prior art.
A method of attaching special purpose lenses and adjusting them to a special wearer presently in use employs a strip of material having one side of a thermosetting adhesive material and another side of a thermoplastic adhesive. See the patent to Blair, U.S. Pat. No. 3,639,044, Feb. 1, 1972. The thermosetting side is placed adjacent the eyeglass frame in the general location desired for the lens and the thermoplastic adhesive abuts the lens itself. In use, the lens is attached to the thermo-plastic part of the strips after heating the strips and attaching the strips to the eyeglass frame. Further heating of the thermosetting side increases the bond between that side and the frame. Once the lens is attached to the thermoplastic side the fit can be checked and, if necessary, the strip reheated to release the bond on the thermoplastic side for adjustment of the len's lateral position. This procedure is repeated as often as necessary to obtain a proper fit.
However, proper fitting in this manner is time-consuming and requires removal of the glasses from the patient's head and the lens from the frame of the glasses in order to reheat the adhesive strips and replace the lens in a new position. This makes reference to the prior position of the lens very difficult for purposes of gauging the desired new location for the lens to achieve proper fit. Once the lens is removed for adjustment it is very difficult to manually adjust the len's lateral position precisely prior to the lens contacting and being again adhesively bound by the thermoplastic side of the strip. This often leads to the need to repeat the adjusting process several times for each lens, resulting in higher cost to the patient for the doctor's or technician's time in making these adjustments, and may decrease the efficiency of the eventual bond of the lens to the frame by the thermoadhesive strips. See also the patent to Lissac, U.S. Pat. No. 3,243,249, Mar. 29, 1966, which discloses securing the lenses to the frame by adhesive coating on a resilient strip.
The problems enumerated in the foregoing paragraphs are not intended to be exhaustive but rather are among many which tend to impair the effectiveness of previously known methods and apparatus for attaching and adjusting lenses, particularly those where the lateral position of the lens is crucial to proper functioning, to the eyeglass frame. Other noteworthy problems may also exist, however, those presented should be sufficient to demonstrate that methods and apparatus for adjusting the lateral position of the lens on the eyeglass frame and positively preventing undesired lateral motion with respect to the frame, after such adjustment, while also facilitating adjustment during the fitting of the lens to the particular wearer appearing in the art have not been altogether satisfactory.